Behaviour of Imidacloprid in Fields. Toxicity for Honey Bees

Following evidence for the intoxication of bees, the systemic insecticide imidacloprid was suspected
from the mid nineties of having harmful effects. Recently, some studies have demonstrated that
imidacloprid is toxic for the bees at sub-lethal doses. These doses are evaluated in the range between
1 and 20 μg kg–1, or less. It appeared thus necessary to study the fate of imidacloprid in the environment
at such low levels. Thus, we developed methods for the determination of low amounts, in
the μg kg–1 range, of the insecticide imidacloprid in soils, plants and pollens using high pressure liquid
chromatography – tandem mass spectrometry (LC/APCI/MS/MS). The extraction and separation
methods were performed according to quality assurance criteria, good laboratory practices and the
European Community’s criteria applicable to banned substances (directive 96/23 EC). The linear concentration
range of application was 1–50 μg kg–1 of imidacloprid, with a relative standard deviation of
2.9% at 1 μg kg–1. The limit of detection and quantification are respectively LOD = 0.1 μg kg–1 and
LOQ = 1 μg kg–1 and are suited to the sub-lethal dose range. This technique allows the unambiguous
identification and quantification of imidacloprid. The results show the remanence of the insecticide in
soils, its ascent into plants during flowering and its bioavailability in pollens.
Key words: imidacloprid, insecticide, Gaucho®, analysis, soils, plants, pollens, bees